California ADU Permit Application Process (2025)

What Is an ADU in California?

An Accessory Dwelling Unit (ADU) is a secondary housing unit on a single-family or multi-family residential property. It can be:
- Detached (a separate building)
- Attached (connected to the main home)
- Converted (from garages, basements, or existing space)
Under recent California laws (SB 9, AB 1033, etc.), ADUs are legal statewide, but local permit processes still apply.

📝 Step-by-Step California Permit Application Process

Step 1: Verify ADU Eligibility

Before applying, confirm your property is zoned to allow ADUs. Key eligibility factors include:

Residential zoning (R1, R2, etc.)
Adequate lot size and setbacks
Available parking (some exemptions apply)
Not located in a coastal or historical overlay zone

Step 2: Prepare Your ADU Plans

To apply for an ADU permit, you'll need detailed architectural and structural plans. Required documents include:

Floor plans and elevations
Site plan with setbacks, property lines, and dimensions
Energy compliance reports (Title 24)
Fire safety and egress information
Sewer and utility access details

Step 3. Submit Your Application

Submit your ADU application to your local city or county building department. Most jurisdictions now support online applications through e-permitting portals like:

LADBS (Los Angeles)
San Diego Development Services
San Jose Building Department
Sacramento and San Francisco portals

Step 4: Plan Review Process

City officials will review your plans for compliance with:

California Building Code (CBC)
Fire and seismic codes
Local development standards
CEQA exemptions (most ADUs are exempt)

Step 5: Pay Permit Fees

ADU permit fees vary by jurisdiction and project type but typically include:

Plan check fee
Building permit fee
Impact or utility connection fees (may be waived for smaller ADUs)

You may pay between $3,000 and $15,000+, depending on the size and scope of your ADU.

Step 6: Permit Approval and Inspections

Once your permit is approved:

You’ll receive official documentation allowing you to start construction
Required inspections include foundation, framing, plumbing, electrical, and final inspection
Upon final approval, you’ll receive a Certificate of Occupancy

⏱️ How Long Does It Take to Get an ADU Permit in California?

Plan preparation: 2–4 weeks

City review process: Up to 60 days (by law)

Revisions & final approval: 1–2 weeks (if needed)

Total estimated timeline: 1.5 to 3 months

💸 How Much Does an ADU Permit Cost in California?

Permit Component	Estimated Cost (2025)
Plan Check Fee	$500 – $2,000
Building Permit Fee	$1,000 – $6,000
Utility Connection Fee	$0 – $4,000 (often waived)
School Impact Fee	Applies if ADU > 750 sq ft
Total Estimate	$3,000 – $15,000+

FAQ

Do I need a permit to build an ADU in California?

Yes. Every ADU must be approved through your local city or county’s permitting process to ensure safety and code compliance.

Can I build an ADU without parking?

In many urban areas, parking requirements are waived if the ADU is near public transit, in a historic district, or part of a home remodel.

Are there limits to ADU size in California?

Generally, yes:

Detached ADUs: Up to 1,200 sq ft
Attached ADUs: Cannot exceed 50% of the main home’s size
Junior ADUs (JADUs): Up to 500 sq ft

How long does it take to get an ADU approved in California?

State law mandates that cities approve or deny ADU permit applications within 60 days, provided all documents are complete.

Can I build both an ADU and a JADU?

Yes, under current California law, homeowners may build one ADU and one Junior ADU (JADU) on the same lot.

Do I need to pay school or impact fees?

Impact and school fees are typically waived for ADUs under 750 square feet. Larger units may be subject to fees based on local ordinances.